Legislators who expressed “serious concerns” about the impact on small businesses nevertheless voted Wednesday to expand sick-leave benefits for employees of some of the city’s smallest companies.

By 46-5, the City Council approved a revised bill that forces businesses with as few as five workers to provide five paid sick days a year.

The bill, expected to quickly be signed into law by Mayor de Blasio, takes effect April 1.

In a small concession to the business community, companies with 19 or fewer workers were granted a six-month grace period on fines.

The bill was the first major piece of legislation passed by the new, left-leaning council, and even members with misgivings went along.

“I’m fearful about our small businesses,” said Councilwoman Inez Dickens (D-Manhattan), who still voted for the measure.

Vincent Ignizio (R-SI) warned that the bill is an unfunded government mandate that would lead to employers paying people under the table.

All three Republicans on the council voted against the measure, along with Democrats Paul Vallone (Queens) and Maria del Carmen Arroyo (Bronx).

In addition to expanding the universe of covered businesses, the bill broadens the definition of family members to include grandchildren, grandparents and siblings whose illnesses would constitute valid excuses for calling in sick and getting paid.